This schematic shows how nanoparticles (blue) injected with water could image the flow of fluid through an oil reservoir’s rocks.

Credit: Advanced Energy Consortium

ILLUMINATING THE RESERVOIR

This schematic shows how nanoparticles (blue) injected with water could image the flow of fluid through an oil reservoir’s rocks.

Credit: Advanced Energy Consortium

Americans guzzle oil in much the same manner that college kids throw back beer at a fraternity party. That is to say, we consume a lot of it. And if one were to take stock of the kegs at a frat house on a Sunday morning, chances are good those silver barrels would hold nothing but dregs.

That’s not the case with oil reservoirs. In fact, anywhere from 30 to 70% of a reservoir’s oil is still underground when a well is considered tapped out. The reason so much precious petroleum gets left behind is that either oil companies can’t locate the oil or it’s stuck within the tiny pores of the reservoir’s rocks.

Now, a consortium of oil companies and oil-field service providers is betting on nano­technology to give a clearer picture of what these reservoirs look like and, with some luck, to help squeeze more oil out of them. The group is known as the Advanced Energy Consortium, or AEC, and it’s managed by the Bureau of Economic Geology, which is part of the University of Texas, Austin.

AEC is the brainchild of Scott W. Tinker, its director. Tinker spent years in the oil and gas industry characterizing reservoirs. About 10 years ago, he attended a workshop where one of the speakers gave a talk on so-called smart dust—nanosized sensor particles for space-based applications. Tinker remembers thinking the concept of smart dust was pretty neat. If he could get his hands on some, perhaps he could use it to better characterize reservoirs. The smart dust could amplify the seismic, acoustic, and electromagnetic signals used to map reservoirs, and perhaps it could slip into those tiny pores of rocks where oil tends to collect.

“It turns out there wasn’t really any smart dust you could buy off the shelf,” Tinker says. “In fact, most of the smart dust was still theoretical at the time.” Still, Tinker thought nanotechnology had something to offer the oil and gas industry, so he set up meetings with the industry’s major players to try to get them interested in ­nanotechnology. Out of that, AEC was born.

At present, AEC includes eight member companies, including oil and gas giants BP, Shell, Total, Petrobras, ConocoPhillips, and BG Group, as well as oil-field service firms Halliburton and Schlumberger. These companies, which compete fiercely in the marketplace, have all come together to fund basic research aimed at developing intelligent sensors and materials that could be injected into oil and gas reservoirs to map such spaces and enhance hydrocarbon recovery. Members of the consortium get a nonexclusive, royalty-free license on any of the research advances the group funds, which they might then take back to their own labs to commercialize for practical use.

“We expect that the demand for energy in all its forms is going to grow by about 50% over the next 40 years or so,” says Sergio Kapusta, chief materials scientist for Shell. “That will require all forms of energy. It will require more oil, more gas, and many other forms of energy.” Along with the increased demand for oil and gas, Kapusta says, oil companies expect that it will be more difficult to find these resources. “Therefore, we are trying to find better ways of finding oil and gas and producing oil and gas. This is where nanotechnology may play a role.”

Tinker and Kapusta both point to the advances the medical community has made in putting small, smart things into the human body. But putting nanosensors in Earth, Tinker says, turns out to be a tougher problem. “Earth has higher pressures, higher temperatures, and it’s much more challenging chemically than the human body,” he says. Also, he points out, we have good ways of visualizing what’s going on in the human body, whereas we don’t have great ways of visualizing what’s happening beneath 10,000 feet of rock.

When AEC put out its first call for proposals in 2008, Tinker says he got a tremendous response from researchers. “These were people that were not working in oil and gas,” he says. “A lot of them didn’t even like the oil and gas industry. But these researchers saw the tremendous challenge.” In the five years since its inception, AEC has raised $38 million to fund 34 projects at more than two dozen universities.

Many of the projects rely on chemical expertise, but physics and engineering also play major roles. “We do not just address how to create a sensing element,” says Carla Thomas, one of AEC’s project managers. “We address the broader issues of deployment of the sensor into the well, transport through the well, retrieval, communication, power, memory, protection of the sensor, and how to handle the resulting data.”

In one AEC project, a team of chemists, physicists, and engineers led by Chun Huh and Keith P. Johnston, a petroleum engineering professor and a chemical engineering professor, respectively, at the University of Texas, Austin, is working to develop superparamagnetic nanoparticles. These particles behave like single independent magnetic domains and could be used as contrast agents in the electromagnetic imaging of reservoirs. The idea is that the particles would be injected into a well, where they’d slip into tiny nooks and crannies of the rock. Once there, they’d be picked up by electromagnetic imaging equipment, giving a more detailed picture of the reservoir underground.

Iron oxide, Johnston says, is a good nanoparticle for such purposes. It’s superparamagnetic, inexpensive, and environmentally benign. The problem, he says, is that iron oxide nanoparticles tend to clump when they encounter the briny conditions in an oil reservoir, where salts can account for up to 10% of the weight of the water underground. “We had to figure out how to get dispersions of magnetic nanoparticles to not crash out at extremely high concentrations of sodium, calcium, and magnesium ions—situations where colloids are normally extremely unstable,” he says.

The key was to develop a coating that would keep these nanoparticles in solution, prevent them from adsorbing to the reservoir’s rock, and also take the particles to the oil-water interface in the reservoir. Johnston and his colleagues recently identified poly(styrene sulfonate-alt-maleic acid) as a coating that could do the job (Langmuir, DOI: 10.1021/la2006327).

They’re even running preliminary tests of the coated nanoparticles on a ranch owned by team member and UT Austin biomedical engineering professor Thomas E. Milner. Although the tests are just in the early stages, Milner and Johnston say they’re encouraged by their results.

“One of our main concerns is obtaining the quantity of nanomaterials required for these proof-of-concept demonstrations,” says Sean Murphy, AEC’s program manager. “So we are having serious discussions with a number of large multinational chemical companies” about supply issues. “As compared to biomedical applications—which use microgram quantities of material—if these tests are successful, the oil and gas industry may soon be ordering contrast-enhancing nanomaterials by the ton.”

In another AEC project,James M. Tour and coworkers at Rice University are developing tracer nanoparticles that would help oil companies quantify how much oil is left in a reservoir.

Oil and gas companies already use tracers in oil reservoirs, injecting them at one end of a reservoir and recovering them at the production site.

But the tracers that companies currently use don’t give any information about oil in the reservoir, Tour says. They tell you only how long it takes the tracer to traverse the length of a reservoir. Ideally, the tracers would provide real-time information about their environments, but developing a sensor that’s smaller than 100 nm in all dimensions, has its own power source, and can communicate through a reservoir’s rock and brine simply isn’t feasible yet.

Tour and his team think they may have struck upon the next best thing—a nanotracer that reports not actively in real time but passively and after the fact on what it encounters in the reservoir. These nano­reporters have cores of oxidized carbon black surrounded by polyvinyl alcohol shells that make the particles water soluble. The researchers stick alkylamine signaling molecules onto the particles via hydrophobic interactions.

The idea is that when the nanoreporter encounters oil, the nanoparticle will release the alkylamine signal into the oil, a phenomenon the scientists can test using mass spectrometry when they recover particles after they have traveled through the reservoir. “If all the signaling molecules are gone, the nanoreporter saw a lot of oil,” Tour explains. “If some are gone, it saw a little oil. If none are gone, it didn’t see any oil.”

The researchers have already done tests using oil-field rock to demonstrate linear losses of signaling molecules depending on the amount of oil in rock (Energy Environ. Sci., DOI: 10.1039/c0ee00237b). They’re hoping to do a field test with the technology sometime this year. What’s more, Tour hopes to tweak the nanoreporters so they might actually help extract oil from existing reservoirs.

“If we can produce 10% more of the oil that we left behind by previous techniques, that would be a very significant amount,” says Shell’s Kapusta. Such oil recovery efforts could produce up to 5 million extra barrels of oil per day. “That’s an enormous amount of oil,” he says.

Kapusta cautions that it’s still early days for AEC. Even so, he already sees the consortium as a success. “We have been able to get many of the best brains in the nanotechnology space to get interested in oil and gas issues,” he says. “The first step to resolving this problem is to get the right people to work on it.”